Shunt flow monitor

ABSTRACT

A shunt including an implantable housing having a proximal end and a distal end. A pressure sensitive valve is contained within the housing at a position between the proximal end and the distal end, and the pressure sensitive valve is capable of controlling a flow of fluid between the fluid inlet port and the fluid outlet port. The shunt further including a sensor assembly fluidly coupled to the pressure sensitive valve, wherein the sensor assembly is mechanically actuated and capable of detecting the flow of fluid through the pressure sensitive valve. A condition of the shunt can be detected by detecting a flow of fluid through the shunt and generating a signal indicative of a period of fluid flow through the implantable shunt based on the detecting. The signal can be output to an external device capable of determining, from the signal, whether the shunt is malfunctioning.

CROSS-REFERENCE TO RELATED APPLICATION

The application claims the benefit of the earlier filing date ofco-pending U.S. Provisional Patent Application No. 61/784,616, filedMar. 14, 2013 and incorporated herein by reference.

BACKGROUND

1. Field

A method and apparatus for detecting a condition of an implantable shuntdevice, more specifically, for detecting a location of a shuntmalfunction. Other embodiments are also described and claimed.

2. Background

A shunt is a surgically implanted device that allows for movement offluid from one part of the body to another. In the case of a cerebralshunt, the shunt diverts cerebrospinal fluid (CSF) from the brain orspine into various body cavities such as the peritoneum, plural space,heart, etc. CSF is produced by the brain and circulates from the brainto the spine and then gets absorbed in the veins. A normal adultproduces between 15-20 cc of CSF per hour. CSF acts as a “cushion” orbuffer for the cortex, providing a basic mechanical and immunologicalprotection to the brain inside the skull and serves a vital function incerebral autoregulation of cerebral blood flow.

When the body fails to properly absorb the CSF, an abnormal accumulationof CSF occurs in the ventricles or cavities within the brain resultingin a medical condition known as hydrocephalus. A cerebral shunt may beimplanted within the patient's brain to help drain the CSF andredistribute it to a different body region for absorption. Cerebralshunts typically consist of three parts: a proximal catheter, a valveand a distal catheter. The proximal catheter is inserted into the brainventricle, which is a site of CSF build up, while the distal catheter ispositioned within any body tissue having enough epithelial cells toabsorb the incoming CSF. Typically, the distal catheter is positionedwithin the peritoneum (where the abdominal organs are located) or thepleural space outside the lungs or the atrium of the heart. The pressuredifferential between the high pressure brain region and the lowerpressure abdomen, lung or atrial region causes the CSF to be drawn intothe proximal catheter and out the end of the distal catheter.

The valve is between the proximal catheter and the distal catheter andis typically positioned behind the ear. The valve is used to control theamount of CSF flowing from the brain to the stomach. When a pressurewithin the brain increases, a pressure level at the valve increasesabove a threshold level (e.g., a low, medium or high pressure) causing agate within the valve to open. CSF can then flow from the brain to theabdomen thereby reducing the pressure level within the brain. Once thepressure drops below the threshold level at the gate, the valve closesthe gate so that CSF flow is stopped. In a fixed pressure setting valve,the pressure threshold level of the valve may be preset prior toplacement of the shunt within the body. Alternatively, the valve may beadjustable such that the threshold level can be changed electronicallyusing a device outside the body without having to remove the shunt.

A working cerebral shunt is critical to patient survival. Cerebralshunts, however, often fail. The failure can be either mechanical orinfectious. In addition, a patient may report symptoms consistent withshunt failure, but in actuality, the shunt is working fine. Since theshunt is implanted within the patient's body, it is difficult todetermine the condition of the shunt and, when there is a failure, whichpart of the stunt requires repair. A computed tomography (CT) scan canbe performed to determine whether the brain is draining properly, butsometimes a CAT scan is inconclusive because the desired region cannotbe viewed properly. In addition, the portion of the shunt in need ofrepair cannot typically be identified from the CAT scan and CSF flowcannot be evaluated. Similar problems arise using x-ray techniques.Other techniques to assess CSF flow through the shunt, such as aradionuclide shuntogram or needle aspiration of the valve reservoir areinvasive, unreliable and non-informative. The patient must thereforeundergo an exploratory shunt surgery so that the surgeon can examine theshunt directly. Exposing the shunt, however, comes with subjecting thepatient to surgical risks and, in addition, a high infection risk to thepatient. In particular, each time a shunt is exposed, there is a 30%chance that within 3 months the patient will get an infection.

BRIEF DESCRIPTION OF THE DRAWINGS

The following illustration is by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate like elements. It should be noted that references to“an” or “one” embodiment in this disclosure are not necessarily to thesame embodiment, and such references mean at least one.

FIG. 1 illustrates a side cross-sectional view of a shunt implantedwithin a subject.

FIG. 2 illustrates a plan view of the shunt illustrated in FIG. 1.

FIG. 3 illustrates a side perspective cut out view of the valve assemblyof FIG. 2.

FIG. 4 illustrates a perspective view of one embodiment of a sensorassembly.

FIG. 5A illustrates a perspective cut out view of one embodiment of avalve assembly.

FIG. 5B illustrates a perspective cut out view of one embodiment of avalve assembly implanted within a patient.

FIG. 6 illustrates a control waveform indicative of a properlyfunctioning shunt.

FIG. 7 illustrates a waveform indicative of a shunt in which no CSF isflowing through the pressure valve.

FIG. 8 illustrates a waveform indicative of a low valve threshold.

FIG. 9 illustrates a waveform indicative of a shunt having a distal endmalfunction.

FIG. 10 illustrates a waveform indicative of a high CSF production rate.

FIG. 11 illustrates a waveform indicative of a proximal end blockage.

FIG. 12 illustrates a waveform indicative of a low rate of CSFproduction.

FIG. 13 illustrates one embodiment of a method for transdermallydetecting a shunt condition.

FIG. 14 illustrates a block diagram of some of the constituentcomponents of an embodiment of an external device.

FIG. 15A illustrates one embodiment of a pressure valve having a sensorassembly integrated therein.

FIG. 15B illustrates one embodiment of the pressure valve of FIG. 15A.

FIG. 16A illustrates another embodiment of a pressure valve having asensor assembly integrated therein.

FIG. 16B illustrates one embodiment of the pressure valve of FIG. 16A.

FIG. 17 represents another method for transdermally detecting a shuntcondition.

DETAILED DESCRIPTION

In this section we shall explain several preferred embodiments withreference to the appended drawings. Whenever the shapes, relativepositions and other aspects of the parts described in the embodimentsare not clearly defined, the scope of the embodiments is not limitedonly to the parts shown, which are meant merely for the purpose ofillustration. Also, while numerous details are set forth, it isunderstood that some embodiments may be practiced without these details.In other instances, well-known structures and techniques have not beenshown in detail so as not to obscure the understanding of thisdescription.

FIG. 1 illustrates a side cross-sectional view of a shunt implantedwithin a subject. Cerebral shunt 102 generally includes a valve assembly104 connected at a proximal end to proximal catheter 106 and a distalend to distal catheter 108. The valve assembly 104 is typicallyimplanted behind the subject's ear. The proximal end of proximalcatheter 106 is positioned within an enlarged ventricle 110 of thesubject and the distal end is connected to valve assembly 104. Theproximal end of distal catheter 108 is connected to the distal end ofvalve assembly 104 and the distal end of distal catheter 108 ispositioned within the peritoneal cavity 112 of the subject. Excess CSFis drawn up into the proximal end of proximal catheter 106, flowsthrough valve assembly 104 and drains out the distal end of distalcatheter 108 into peritoneal cavity 112. The direction of CSF flow isillustrated by arrow 114. Although distal catheter 108 is shownpositioned within peritoneal cavity 112, it may also be positionedwithin another body cavity capable of absorbing CSF.

FIG. 2 illustrates a plan view of the shunt illustrated in FIG. 1. Shunt102 includes valve assembly 104, proximal catheter 106 and distalcatheter 108. Proximal catheter 106 is fluidly connected to proximal end202 of valve assembly 104 by proximal valve tube 242. Similarly, distalcatheter 108 is fluidly connected to distal end 204 of valve assembly104 by distal valve tube 244. Proximal valve tube 242 and distal valvetube 244 help to regulate CSF flow into and out of valve assembly 104.Representatively, each of proximal valve tube 242 and distal valve tube244 may be one-way valves that are one way in a direction of CSF flow114.

Valve assembly 104 includes an outer housing formed by a base member 240and a cover member (removed for illustration purposes). Base member 240includes channel 206 formed along its length from the proximal end 202to the distal end 204. CSF flowing into valve assembly 104 from proximalvalve tube 242 flows through channel 206 in the direction of arrow 114to the distal end 204 of valve assembly 104. Channel 206 may have anysize and dimensions suitable for accommodating a desired amount of CSFflow.

Valve assembly 104 further includes one-way valve 208, reservoir 210,pressure valve 214, sensor assembly 216 and anti-siphon member 218mounted along base member 240. Each of these components is in fluidcommunication with channel 206 and help to regulate and/or monitor CSFflow through valve assembly 104.

In one embodiment, one-way valve 208 may be an optional valve positionedat the proximal end 202 of valve assembly 104. One-way valve 208 may beany type of one-way valve capable of allowing CSF to flow into valveassembly 104 in a direction of CSF flow 114 and preventing CSF flow inan opposite direction.

Reservoir 210 may be at a position downstream from one-way valve 208along CSF channel 206. Reservoir 210 serves several important functions.Reservoir 210 can be used to remove samples of CSF for testing using aneedle or a syringe. Fluids may also be injected into reservoir 210 andflushed through valve assembly 104 to test for flow and ensure properfunctioning of shunt 102. Reservoir 210 may therefore be formed of anymaterial that can be pierced by a needle or syringe, for example apolymer material. In one embodiment, reservoir 210 may be a bulb shapedstructure formed of a rubber material.

Pressure valve 214 may be at a position downstream from reservoir 210,also along CSF channel 206. Pressure valve 214 may be used to moderatethe pressure or flow rate of CSF through valve assembly 104. Pressurevalve 214 may be any type of pressure valve suitable for use in a shuntsystem. For example, pressure valve 214 may be a high pressure, mediumpressure, low pressure or low-low pressure valve such as thosecommercially available from Medtronic Inc. Pressure valve 214 may beprogrammable, meaning that its pressure settings can be changed remotelyafter implantation or fixed, meaning that its pressure settings arefixed once implanted within the body. Pressure valve 214 includes a gatewhich, at a certain threshold pressure, either opens to allow CSF flowor closes to prevent CSF flow through valve assembly 104. For example,when the CSF pressure within valve assembly 104 is above a predeterminedthreshold value, the gate opens so that CSF can flow through pressurevalve 214 and out distal end 204 of valve assembly 104. CSF flow throughpressure valve 214 reduces the pressure within valve assembly 104. Oncethe pressure is below the set threshold, the gate closes and CSF flow tothe distal end 204 stops.

Anti-siphon member 218 is positioned at the distal end 204 of valveassembly 104. Anti-siphon member 218 may be optional, and when included,may be any type of anti-siphoning device capable of preventing CSF frombeing drawn into valve assembly 104 through the distal end.

Sensor assembly 216 is positioned between pressure valve 214 andanti-siphon member 218. In this aspect, sensor assembly 216 is distal toor downstream from pressure valve 214. Sensor assembly 216 can thereforedetect CSF flow through pressure valve 214. In this aspect, sensorassembly 216 can be used to indirectly monitor the activity of pressurevalve 214. The activity of pressure valve 214 can be used to identify alocation of any malfunctions within shunt 102 as will be described inmore detail in reference to FIG. 6 to FIG. 12.

Sensor assembly 216 is designed so that information corresponding to theactivity of pressure valve 214, and in turn a condition of shunt 102,can be obtained by the care provider transdermally (a non-invasivemethod). This provides advantages over current detection procedures. Inparticular, as previously discussed, shunt malfunction is difficult toconfirm non-invasively and it is even more difficult to identify whichportion of the shunt is malfunctioning without performing an exploratorysurgical procedure. These exploratory surgical procedures are not onlyinvasive and uncomfortable for the patient subjecting the patient tosurgical risks, they significantly increase the likelihood of patientinfection including but not limited to meningitis. Sensor assembly 216therefore provides invaluable information in a non-invasive manner,which significantly reduces patient risks. Moreover, in one embodiment,sensor assembly 216 is mechanically actuated, in other words it isactuated by rotation of rotor assembly 220 and does not require abattery for operation. Since sensor is mechanically actuated, surgicalintervention to replace a battery associated with the shunt is avoided.It is contemplated, however, that in some embodiments, a battery may beused to actuate one or more of valve assembly 104 components. In anotherembodiment described in reference to FIG. 15A and FIG. 15B, amicroprocessor recording and an RFID detection mechanism may be used forthis purpose.

Sensor assembly 216 will now be described in detail. In one embodiment,sensor assembly 216 includes a rotor assembly 220, a generator assembly224 and a primary induction coil 226. The rotor assembly 220 isrotatably coupled to base member 240 and is within the flow path of CSFflowing through channel 206. As CSF flows in direction 114 throughchannel 206, rotor assembly 220 rotates. Rotation of rotor assembly 220causes a rotor (not shown) within generator assembly 224 to rotate.Generator assembly 224 converts this mechanical energy into anelectrical pulse, which is transmitted through one or more of conductingwires 228, 230 to primary induction coil 226, also mounted on basemember 240. Primary induction coil 226 generates a magnetic pulsecorresponding to the electrical pulse output by generator assembly 224.This magnetic pulse is then detected through transdermal coupling by asecondary induction coil positioned within an external device.

The external device may be, for example, a hand-held signal processingmember as will be described in more detail in reference to FIG. 5B. Thehand-held signal processing member may be any external electronic devicecapable of processing one or more signals output by sensor assembly 216,processing the signal and displaying to a user whether a malfunction inthe shunt has occurred and if so, the location of the malfunction. Forexample, the external device may be any type of mobile device having adisplay capable of displaying information to the user.

Alternatively, the external device may simply detect the signals outputby sensor assembly 216 and transmit the signals to a separate displayand/or computing device that can display the shunt condition. Forexample, the external device may be a probe, or similar device, that isconnected to a patient monitor capable of displaying information to thecare provider. When the probe, which contains the secondary inductioncoil, is transdermally coupled to the shunt, it reads the signal outputby sensor assembly 216 and transmits it to the display device. Thedisplay device may be, for example, a computer, having a processingprogram that can process signals from the probe and display theassociated shunt condition information on the display.

It is noted that although in one embodiment, sensor assembly 216 ispositioned between pressure valve 214 and anti-siphon member 218, it maybe positioned at other regions of valve assembly 104 to monitor fluidflow through valve assembly 104. For example, sensor assembly 216 couldbe positioned proximal to pressure valve 214. In any case, since theposition of sensor assembly 216 relative to the other valve assemblycomponents 104 is known, the output signal can be evaluated andinterpreted to determine a condition of shunt 102, and in particular, alocation of a malfunction.

FIG. 3 illustrates a side perspective cut out view of the valve assemblyof FIG. 2. Cover member 302 is shown removed from base member 240 sothat the internal components can be viewed. When cover member 302 isattached to base member 240, the two structures form a housing thatencases each of the components attached to base 240. Fluid inlet port304 may be formed in proximal end 202 and fluid outlet port 306 formedin the distal end 204. The tube portion of proximal valve tube 242 mayenter the housing through fluid inlet port 304 and connect to one-wayvalve 208. Distal valve tube 244 enters the housing through fluid outletport 306 and connects to anti-siphon member 218. CSF from proximalcatheter 106 enters valve assembly 104 through fluid inlet port 304 toone-way valve 208. One-way valve 208 outputs the CSF into channel 206.CSF flows along channel 206 to reservoir 210, pressure valve 214, sensorassembly 216 and finally to anti-siphon member 218. Anti-siphon member218 outputs CSF through distal valve tube 244 within fluid outlet port306 so that it can travel through distal catheter 108 to the desiredbody cavity.

In some embodiments, fluid inlet port 304 and/or fluid outlet port 306are holes formed entirely through the wall of cover member 302. In otherembodiments, fluid inlet port 304 and/or fluid outlet port 306 are slotsformed along the bottom edge of cover member 302. When cover member 302is placed on base member 240, the holes or slots align with channel 206so that fluid can enter valve assembly 104 and flow along channel 206from the proximal end 202 to the distal end 204.

FIG. 4 illustrates a perspective view of one embodiment of a sensorassembly. As previously discussed, sensor assembly 216 may include rotorassembly 220 connected to generator assembly 224, which is in turnconnected to primary induction coil 226. Rotor assembly 220 may be asubstantially planar, disc shaped structure having recesses 402 aroundits circumferential wall. Rotor assembly 220 is mounted along basemember 240 so that CSF flowing though channel 206 catches on recesses402 causing rotor assembly 220 to rotate in the direction of CSF flow asillustrated by arrow 404. It is noted that the bearings used to mountrotor assembly 220 are outside of CSF flow therefore preventingmalfunction of rotor assembly 220 due to CSF build up about thebearings.

Rotor assembly 220 is mechanically connected to generator assembly 224such that rotation of rotor assembly 220 drives rotation of a rotorwithin generator assembly 224. Generator assembly 224 outputs thismechanical energy as an electrical pulse or voltage. This electricalpulse is transmitted through one or more of conducting wires 228, 230 toprimary induction coil 226. Primary induction coil 226 generates amagnetic pulse corresponding to the electrical pulse output by generatorassembly 224. Accordingly, for every electrical pulse output bygenerator assembly 224, a corresponding magnetic pulse or signal isoutput by primary induction coil 226.

This magnetic pulse is then detected through transdermal coupling by asecondary induction coil positioned within an external device. Tofacilitate coupling and alignment of primary induction coil 226 with theexternal secondary induction coil, cover member 302 may have a recessportion 510 formed within a portion of the outer wall as illustrated inFIG. 5A. Recess portion 510 may be positioned near primary inductioncoil 226. When external device 502 is positioned within recess portion510, as illustrated in FIG. 5B, secondary induction coil 508 issubstantially aligned with primary induction coil 226. In this aspect,recess portion 510 may be of any size and shape capable of aligningprimary induction coil 226 with secondary induction coil 508.

To further facilitate alignment, secondary induction coil 508 may bepositioned within a portion of external device 502 that is complimentaryto, and can easily be aligned within, recess portion 510.Representatively, external device 502 may be formed by a housing 504having a protruding portion 506 complimentary to the shape of recessportion 510 so that it can rest within recess portion 510. When valveassembly 104 is implanted between the external skin layer 512 and theinternal brain tissue 514, the user can digitally examine the valveassembly 104 and identify recess portion 510 through external skin layer512. Once recess portion 510 is identified, pressing of external device502 against recess portion 510 ensures that primary induction coil 226and secondary induction coil 508 are properly aligned.

As previously discussed, the external device may include a signalprocessing member that can process the signals output by sensor assembly216 and identify to a user whether a malfunction in the shunt hasoccurred and if so, the location of the malfunction. In this aspect,hand-held device may include display 514 to display the processingresults in any number of ways. In one embodiment, display 514 may be anLCD alphanumeric display or any other type of display capable ofcommunicating a malfunction to a user. For example, display 514 mayindicate that the shunt is malfunctioning and/or may identify thespecific location of the malfunction. Representatively, display 514 mayindicate to the user that the malfunction is at the location of any ofthe internal components. For example, display 514 can indicate to theuser that the proximal catheter is blocked, the distal catheter isblocked or that the pressure valve is malfunctioning, for example, thevalve setting is too low or too high. It should further be understoodthat any signals (also referred to as information or communicationsherein) output by sensor assembly 216 and/or information as to whether amalfunction has occurred may be recorded and stored for later analysis.

It is further contemplated that in some embodiments the external devicecould be a patch connected to a lead, which is in turn connected to anon-mobile or mobile computing device, such as device 502.Representatively, the patch may have an adhesive side which sticks tothe external skin layer 512 at a position near recess portion 510 andthe opposite side may be connected to a lead. The signals output bysensor assembly 216 may be transmitted along the lead to the associatedcomputing device for processing and, in some cases, recording. In thisaspect, the shunt condition may be continuously or periodicallymonitored without the presence of a health care provider and/or someoneto manually align and hold the device near sensor assembly 216 whenmonitoring is required.

The algorithms for identifying an overall condition of the shunt and/ormalfunction from the signals output by the sensor assembly 216 will nowbe discussed in reference to FIG. 6-FIG. 12.

As previously discussed, pressure valve 214 has a predetermined pressurethreshold and therefore controls whether CSF flows through valveassembly 104. If pressure valve 214 has a low threshold setting, it mayonly take a relatively low pressure for pressure valve 214 to open andallow CSF flow. Alternatively, pressure valve 214 may have a highthreshold setting such that a relatively high pressure is required toopen pressure valve 214 and allow CSF flow. Sensor assembly 216 ispositioned downstream from pressure valve 214, in other words betweenpressure valve 214 and distal end 204. Thus, any CSF flow throughpressure valve 214, or a lack of fluid flow, is detected and monitoredby sensor assembly 216. Sensor assembly 216 outputs a correspondingsignal that can be detected by secondary induction coil 508 withinexternal device 502. The signal detected by secondary induction coil 508may be represented as a square waveform that is indicative of thepresence of CSF flow distal to pressure valve 214 and the length of timethe fluid is flowing. The square waveform, and/or the information usedto generate the square waveform, may be used to determine a shuntmalfunction by comparing the waveform and/or information to a control.The control may be specific to a particular patient or may be astandardized control preprogrammed into the external device during amanufacturing operation. In the case of a control specific to thepatient, the control values may be determined shortly after shuntplacement within the patient and then saved for future use.

FIG. 6 illustrates a control CSF waveform indicative of a properlyfunctioning shunt. The y-axis represents a voltage measurement and thex-axis represents time. Each wave 604 represents a voltage increasecaused by CSF flow past sensor assembly 216. CSF flows past sensorassembly 216 when pressure valve 214 is open. Thus, the period of timeover which wave 604 occurs, in other words the width of wave 604, isproportional to the length of time pressure valve 214 remains open. Thisperiod 606 within which pressure valve 214 remains open may be referredto herein interchangeably as the wave period, the open valve period, thefluid flow period or the wave width. Thus, the longer pressure valve 214remains open, the wider wave 604 will be.

Area 608 between waves 604 represents a substantially zero or lowvoltage area which corresponds to the period of time over which no CSFis flowing past sensor assembly 216, in other words, pressure valve 214is closed and no CSF is flowing through the valve. Area 608 may bereferred to herein interchangeably as the period between waves, betweenwave period, the closed valve period, the no-flow period or zero or lowvoltage period. The wave period 606 along with the between wave period608 can be used to indirectly evaluate the activity of pressure valve214 and in turn, a condition of the shunt. Waveform 602 is a controlwaveform indicative of a properly functioning shunt that is allowing forCSF flow at consistent and regular intervals.

FIG. 7 illustrates a CSF waveform indicative of a shunt in which no CSFis flowing through the pressure valve. In particular, waveform 702 has aconstant substantially zero or low voltage. The constant zero or lowvoltage indicates one of two scenarios. The first being that there is acomplete blockage of the shunt, i.e., no CSF is flowing through theshunt therefore pressure valve 214 remains closed. Alternatively, theconstant zero or low voltage could indicate that CSF production is belowthe threshold of pressure valve 214 and therefore pressure valve 214remains closed. The external device 502 can display to the user that oneof the two scenarios is occurring. The user can then use thisinformation to determine the appropriate course of action. For example,the user may decrease the pressure valve threshold so that a lower CSFpressure is required to open pressure valve 214. After a period of time,the user can then take a second reading. If the second reading resultsin a waveform more consistent with the control waveform 602, the usercan determine that it was the threshold setting that needed to beadjusted. If the reading remains the same, in other words pressure valve214 remains closed even at a lower pressure setting, the user maydetermine that the malfunction is a complete blockage of the shunt andthat the shunt needs to be surgically repaired.

FIG. 8 illustrates a waveform indicative of a low valve threshold. Inparticular, waveform 802 illustrates a constant (non-pulsatile) voltage.This indicates that CSF pressure valve 214 is continuously open andtherefore CSF is constantly flowing past pressure valve 214. A constantCSF flow indicates that the valve threshold setting may be too low andallowing an unnecessarily large amount of CSF to drain. The externaldevice 502 would therefore display to the user that the valve thresholdis low. Based on this information, the user can increase the pressurethreshold of pressure valve 214 and take a second reading. If the secondreading indicates a more pulsatile voltage comparable to controlwaveform 602, the user can verify it was the threshold setting thatneeded to be adjusted and that surgical repair is not necessary. If thereading remains the same, the user may determine that the malfunction isthe pressure valve 214 and proceed with surgical intervention.

FIG. 9 illustrates a waveform indicative of a shunt having a distal endmalfunction. In particular, waveform 902 illustrates a wave 904 having awave period 906 less than that of the control waveform 602 and also abetween wave period 908 less than that of the control waveform 602. Inother words, there is a bottleneck at the region of shunt valve assembly202 distal to sensor assembly 216. This bottleneck causes pressure tobuild up within the area of valve assembly 104 distal to pressure valve214. Pressure valve 214 does not open unless the difference between apressure at its proximal end and distal end is greater than thepredetermined pressure valve threshold setting. If the pressure at thedistal end of pressure valve is greater than a pressure at a proximalend of pressure valve 214, pressure valve 214 closes. Alternatively, ifthe pressure at the distal end is less than the pressure at the proximalend and the difference between the two is greater than the pressurethreshold setting of pressure valve 214, pressure valve 214 opens. Assuch, in the case of a distal blockage, pressure valve 214 may initiallyopen to allow CSF flow; the CSF quickly begins to build up at the distalend, thus rapidly increasing a pressure at the distal end of pressurevalve 214 above the pressure at its proximal end. This causes pressurevalve 214 to close and CSF flow past pressure valve 214 to stop. CSF,however, is still flowing into the proximal end of valve assembly 104and building up at the proximal end of pressure valve 214. In turn, thedistal blockage may not be a complete blockage therefore the pressurelevel distal to valve 214 may be slowly decreasing to the point wherethe difference between the proximal end pressure and distal end pressureof pressure valve 214 is once again greater than the threshold pressurevalue of pressure valve 214. Pressure valve 214 in turn opens, butagain, only briefly before it closes again and prevents CSF flow pastpressure valve 214, because the distal pressure continues to quicklybuild. As a result of these occurrences, waveform 902 having waveperiods 906 (i.e., open valve periods) which are narrower (i.e., shorterduration) than that of control 602 and between wave periods 908 (i.e.,closed valve periods) which are closer (i.e., shorter duration) thancontrol 602.

Based on this information, the external device 502 would display to theuser that the shunt distal end is malfunctioning. The care providershould therefore repair the anti-siphon member 218, distal valve tube244 or possibly the distal catheter 108. Although the specific componentwithin the distal end may not be identified, such information is notnecessary for surgical intervention. In particular, regardless of whichdistal end component is malfunctioning, surgical repair of any of thecomponents can be achieved by one incision at the distal end. Thus,identification of the specific component prior to surgery is notnecessary. It is contemplated, however, that it may be possible tolocate the specific component that is malfunctioning by takingadditional readings. For example, the settings of valve 214 may bemodified and further readings taken to further identify the point ofmalfunction.

FIG. 10 illustrates a waveform indicative of a high CSF production rate.In particular, waveform 1002 illustrates a wave 1004 having a waveperiod 1006 greater than that of the control waveform 602 and also abetween wave period 1008 less than that of the control waveform 602. Inother words, pressure valve 214 is remaining open for longer periods oftime than that of the control and closing for shorter periods of time.This indicates a high CSF production rate because when the CSFproduction rate is high, CSF continues to flow into valve assembly 104and to pressure valve 214. Once the pressure at pressure valve 214 isabove the predetermined threshold value, pressure valve 214 opens torelieve the pressure but CSF continues to flow into valve assembly 104thus requiring pressure valve 214 to remain open for a longer period oftime to reduce the pressure below the threshold. Once the pressure isreduced below the threshold pressure level, pressure valve 214 closesbut only for a short period of time before the pressure level increasesagain causing pressure valve 214 to open. As a result of theseoccurrences, waveform 1002 having wave periods 1006 (i.e., open valveperiods) which are wider (i.e., longer duration) than that of control602 and between wave periods 1008 (i.e., closed valve periods) which arecloser (i.e., shorter duration) than control 602.

Based on these results, the external device 502 would display to theuser that the CSF production rate is high. This indicates to the userthat the pressure valve threshold level should be reduced to allow fordraining of more CSF.

FIG. 11 illustrates a waveform indicative of a proximal end blockage. Inparticular, waveform 1102 illustrates a wave 1104 having a wave period1106 less than that of the control waveform 602 and a between waveperiod 1108 greater than that of the control waveform 602. In otherwords, pressure valve 214 is remaining open for shorter periods of timethan that of the control and closing for longer periods of time. Thisindicates a proximal end blockage because when the proximal end is fullyor partially blocked, there is no, or only a small amount in the case ofa partial blockage, of CSF flow into valve assembly 104 and to pressurevalve 214. It therefore takes a relatively long time for a pressurelevel proximal to pressure valve 214 to build to a level above thepredetermined pressure threshold setting of pressure valve 214 and causepressure valve 214 to open. Once pressure valve 214 does open, itrequires a relatively short period of time for CSF to drain and causethe pressure to drop below the threshold level. As a result, waveform1102 has wave periods 1106 (i.e., open valve periods) which are narrower(i.e., shorter duration) than that of control 602 and between waveperiods 1108 (i.e., closed valve periods) which are longer (i.e., longerduration) than control 602.

Based on these results, the external device 502 would display to theuser that there is a proximal end blockage. This indicates to the userthat one of the components proximal to pressure valve 214 is in need ofrepair. For example, reservoir 210, one-way valve 208, proximal valve206 or proximal catheter 106. Since the surgeon now knows the generallocation of malfunction, a single incision at the proximal end of valveassembly 104 can be made and any of the above-referenced proximalcomponents accessed through the single incision for repair.

FIG. 12 illustrates a waveform indicative of a low rate of CSFproduction. In particular, waveform 1202 illustrates a wave 1204 havinga wave period 1206 greater than that of the control waveform 602 and abetween wave period 1208 greater than that of the control waveform 602.In other words, pressure valve 214 is remaining open for longer periodsof time than that of the control and closing for longer periods of time.This indicates a low rate of CSF production. As a result, waveform 1202has wave periods 1206 (i.e., open valve periods) which are longer (i.e.,longer duration) than that of control 602 and between wave periods 1208(i.e., closed valve periods) which are longer (i.e., longer duration)than control 602.

Based on these results, the external device 502 would display to theuser that CSF production rate is low. This indicates to the user thatthe pressure threshold level of pressure valve 214 should be increased.The care provider may therefore increase the threshold level without theneed for an invasive exploratory procedure.

Table 1 below illustrates each of the above-described algorithms andexemplary actions that could be taken in response to the readingsdisplayed on external device 502.

TABLE 1 Period between waves Period of wave Algorithm (pressure valveclosed) (pressure valve open) Shunt Condition Action 1 Same as controlSame as control Properly None (FIG. 6) functioning 2 No wave No waveComplete Decrease (FIG. 7) blockage; or pressure valve no CSF productionthreshold and beyond pressure take second valve threshold reading 3 NoneGreater than control Low pressure Increase (FIG. 8) valve thresholdpressure valve setting threshold 4 Less than control Less than controlDistal end Repair distal (FIG. 9) malfunction end (e.g. anti- siphonmember and/or distal catheter) 5 Less than control Greater than controlHigh CSF Decrease (FIG. 10) production rate pressure valve threshold 6Greater than control Less than control Proximal end Repair (FIG. 11)malfunction proximal end (e.g. reservoir, one-way valve, proximal valve,or proximal catheter) 7 Greater than control Greater than control LowCSF Increase (FIG. 12) production rate pressure valve threshold

One representative method for transdermally detecting a shunt conditionis illustrated in FIG. 13. In one embodiment, the external device isused to transdermally detect a signal from the shunt sensor assembly(block 1302). The signal may be output by the previously describedsensor assembly which detects a flow of fluid through the shunt andgenerates a signal indicative of a period of fluid flow. Once the signalis detected, any one or more of the previously described algorithms isapplied to determine the shunt condition (block 1304). For example, theexternal device, or a display device coupled to the external device, mayinclude a signal processing program that can process the signalaccording to the previously discussed algorithms to determine the shuntcondition. The shunt condition is displayed to the user on the display(block 1306). Based on the displayed shunt condition, the user candetermine the appropriate course of action.

FIG. 14 illustrates a block diagram of some of the constituentcomponents of an embodiment of an external device within which thepreviously described signal and algorithm can be processed. Device 1402may be any one of several different types of electronic devices that canbe easily held in the user's hand during normal use. In particular, thedevice 1400 may be any mobile device, such as a cellular phone, a smartphone, or a tablet-like portable computer. In one embodiment, device1400 is an external device such as external device 502 illustrated inFIG. 5B.

In this aspect, external device 1400 includes a processor 1412 thatinteracts with storage 1408, memory 1414, display 1422, and user inputinterface 1424. Main processor 1412 may also interact withcommunications circuitry 1402 and primary power source 1410. The variouscomponents of the external device 1400 may be digitally interconnectedand used or managed by a software stack being executed by the processor612. Many of the components shown or described here may be implementedas one or more dedicated hardware units and/or a programmed processor(software being executed by a processor, e.g., the processor 1412).

The processor 1412 controls the overall operation of the device 1400 byperforming some or all of the operations of one or more applications oroperating system programs implemented on the device 1400, by executinginstructions for it (software code and data) that may be found in thestorage 1408. The processor may, for example, drive the display 1422 andreceive user inputs through the user input interface 1424 (which may beintegrated with the display 1422 as part of a single, touch sensitivedisplay panel). In addition, processor 1412 may process the signalreceived from the secondary induction coil positioned within externaldevice 1400 according to the previously described algorithms.

Storage 1408 provides a relatively large amount of “permanent” datastorage, using nonvolatile solid state memory (e.g., flash storage)and/or a kinetic nonvolatile storage device (e.g., rotating magneticdisk drive). Storage 1408 may include both local storage and storagespace on a remote server. Storage 1408 may store and record data as wellas software components that control and manage, at a higher level, thedifferent functions of the device 1400.

In addition to storage 1408, there may be memory 1414, also referred toas main memory or program memory, which provides relatively fast accessto stored code and data that is being executed by the processor 1412.Memory 1414 may include solid state random access memory (RAM), e.g.,static RAM or dynamic RAM. There may be one or more processors, e.g.,processor 1412, that run or execute various software programs, modules,or sets of instructions (e.g., algorithms 1-7 of Table 1) that, whilestored permanently in the storage 1408, have been transferred to thememory 1414 for execution, to perform the various functions describedabove.

The device 1400 may include communications circuitry 1402.Communications circuitry 1402 may include components used for wired orwireless communications, such as two-way conversations and datatransfers. For example, communications circuitry 1402 may include Wi-Ficommunications circuitry so that the user of the device 1400 maytransfer data through a wireless local area network.

Device 1400 also includes primary power source 1410, such as a built inbattery, as a primary power supply. Alternatively, power source 1410 mayderive power from an alternating current (AC) power supply in abuilding, such as through a cord, Wi Fi signal, solar source or otherexternal power source.

In still further embodiments, the external device may be a non-mobileexternal device, for example, a desk top computer, desk top monitor ortelevision. Similar to device 1400, the non-mobile external device mayinclude a processor that interacts with, a storage unit, memory unit,display, user input interface and communications circuitry. Thenon-mobile external device may further interact with a probe type devicehaving secondary induction coil which can be used to receive the signalfrom the primary induction coil positioned within the valve assembly.The various components of the external device may be digitallyinterconnected and used or managed by a software stack being executed bythe main processor. Many of the components shown or described here maybe implemented as one or more dedicated hardware units and/or aprogrammed processor (software being executed by a processor, e.g., themain processor).

FIG. 15A and FIG. 15B illustrate an embodiment of a pressure valvehaving a sensor assembly integrated therein. Pressure valve 1500 may beone example of the pressure valve 214 which can be integrated withinshunt 102 as previously described in reference to, for example, FIG. 2and FIG. 3. In this embodiment, pressure valve 1500 may include a sensorintegrated therein such that a separate sensor assembly (e.g. sensorassembly 216) can be omitted. Representatively, pressure valve 1500 mayinclude a sensor such as a passive radio frequency identification (RFID)tag 1502 positioned within housing 1504 of valve 1500. Tag 1502 is usedto communicate the status of the shunt externally. Representatively, tag1502 can be powered by an external device having an active reader (e.g.device 502 having an active reader or any of the other previouslydiscussed external devices) configured to broadcast at the excitationfrequency of tag 1502. The active reader transmits interrogator signalsand also receives authentication replies (i.e. communications) from tag1502. Tag 1502 includes broadcasting circuitry 1506 which is broken (oropen) when the valve gate 1508 is in the closed position (i.e. no CSF isflowing through valve 1500) and closed when valve gate 1508 is in theopen position (i.e. CSF is flowing through valve 1500). Valve gate 1508may be pressure sensitive such that pressure on valve gate 1508 from CSFflow in the direction of arrow 1512 causes the valve gate 1508 to eitheropen (when the pressure is great enough) or close (when the pressure isnot great enough). The status and/or malfunction of the shunt in whichpressure valve 1500 is incorporated (e.g. shunt 102) can be determinedbased on the RFID tag signal indicating whether the valve gate 1508 isopen (CSF flow) or closed (no CSF flow) using any one or more of thepreviously discussed algorithms.

For example, in one embodiment, valve gate 1508 may be a tension springconnected to an electrical circuit of tag 1502. When the spring isdisplaced due to flow of CSF in the direction of arrow 1512 (asillustrated in FIG. 15B) through the valve input tube 1510, the springcontacts an electrical contact 1516 of tag 1502, closing thebroadcasting circuit of tag 1502 and allowing its signal to be read bythe external reader. When the signal is output from tag 1502 to thereader, the reader (or an associated computing device) interprets thisinformation to mean that valve gate 1508 is open and CSF is flowingthrough the valve. FIG. 15A illustrates valve gate 1508 in the closedposition such that CSF cannot flow into valve housing 1504, and in turnno signal is output from tag 1502 to the reader. When no signal isoutput from tag 1502 to the reader, the external reader device (or anassociated computing device) interprets this information to mean thatvalve gate 1508 is closed and no CSF is flowing through valve 1500. Anyone or more of the previously discussed algorithms in Table 1(illustrated in FIGS. 6-12) are then used to determine a malfunctionand/or status of the shunt.

FIG. 16A and FIG. 16B illustrate another embodiment of a pressure valvehaving a sensor assembly integrated therein. Valve 1600 is substantiallysimilar to valve 1500 described in reference to FIG. 15A-15B except inthis embodiment, valve 1600 is a ball valve having a ball 1602, whichpresses against valve gate 1508, and in turn, opens valve gate 1508 whenCSF flow causes a sufficient pressure against ball 1602.Representatively, as illustrated in FIG. 16A, ball 1602 is in front ofvalve gate 1508 such that CSF flow in the direction of arrow 1512 causesball 1602 to press against valve gate 1508. Valve gate 1508, however,remains closed because there is insufficient pressure to open it. Aspreviously discussed, when valve gate 1508 is closed, the circuit ofRFID tag 1502 is open and therefore tag 1502 does not output a signal tothe external reader device. Once a pressure against the ball 1602 due toCSF flow reaches a threshold level, however, the pressure of ball 1602against valve gate 1508 causes valve gate 1508 to open, and in turn,complete the circuit with RFID tag 1502 such that a signal is output tothe external reader device.

Each of pressure valve 1500 and 1600, and any of the other pressurevalves disclosed herein, may be programmable valves in which thepressure setting of the gate can be changed or fixed valves having afixed pressure setting. In addition, it should be understood thatpressure valves 1500 and 1600 provide a unique advantage in that sincethey have an RFID tag sensor integrated therein, in addition to beingable to be monitored externally, they can be monitored from a distance(i.e. several meters) and no alignment or direct contact of the readerdevice with the patient and/or shunt is required. It is further to beunderstood that although tag 1502 is described as a passive RFID tag, itis contemplated that an active RFID tag may be used and the reader maybe a passive reader or an active reader.

FIG. 17 represents another method for transdermally or non-invasivelydetecting a shunt condition. In one embodiment, an external device (e.g.mobile device having an RFID tag reader or patch) is used totransdermally detect a signal from an RFID tag integrated within a shuntpressure valve (block 1702). A signal indicating whether the pressurevalve is open or closed may be output by the RFID tag. Once the signalis detected, any one or more of the previously described algorithms ofTable 1 is applied to determine the shunt condition (block 1704). Forexample, the external device, or a display device coupled to theexternal device, may include a signal processing program that canprocess the signal according to the previously discussed algorithms todetermine the shunt condition. The shunt condition is displayed to theuser on the display (block 1706). Based on the displayed shuntcondition, the user can determine the appropriate course of action.

It is further to be understood that the external device, such as device502, for performing the operations herein may be specially constructedfor the required purposes or it may comprise a general purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a computerreadable storage medium, such as, but not limited to, any type of diskincluding floppy disks, optical disks, CD-ROMs and magnetic-opticaldisks, read-only memories (ROMs), random access memories (RAMs), EPROMs,EEPROMs, magnetic or optical cards, Flash memory devices includinguniversal serial bus (USB) storage devices (e.g., USB key devices) orany type of media suitable for storing electronic instructions, each ofwhich may be coupled to a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general purposesystems may be used with programs in accordance with the teachingsherein or it may prove convenient to construct a more specialized deviceto perform the described method. In addition, the invention is notdescribed with reference to any particular programming language. It willbe appreciated that a variety of programming languages may be used toimplement the teachings of the invention as described herein.

A computer readable medium includes any mechanism for storinginformation in a form readable by a computer. For example, a computerreadable medium includes read only memory (“ROM”), random access memory(“RAM”), magnetic disk storage media; optical storage media, flashmemory devices or other type of machine-accessible storage media.

In the preceding detailed description, specific embodiments aredescribed. It will, however, be evident that various modifications andchanges may be made thereto without departing from the broader spiritand scope of the claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than restrictivesense.

What is claimed is:
 1. A shunt system comprising: an implantable housinghaving a proximal end and a distal end, wherein a fluid inlet port isformed in the proximal end and a fluid outlet port is formed in thedistal end; a pressure sensitive valve contained within the housing at aposition between the proximal end and the distal end, the pressuresensitive valve capable of controlling a flow of fluid between the fluidinlet port and the fluid outlet port; and a sensor assembly fluidlycoupled to the pressure sensitive valve, wherein the sensor assembly ismechanically actuated and capable of detecting the flow of fluid throughthe pressure sensitive valve.
 2. The shunt system of claim 1 wherein thesensor assembly comprises a rotor coupled to a generator, wherein therotor rotates as fluid flows through the pressure sensitive valve andthe generator generates a signal indicative of the flow of fluid throughthe rotor.
 3. The shunt system of claim 2 wherein the signal is amagnetic pulse, and the shunt system further comprises: an externaldevice that detects the signal and, based on the signal, displays theshunt condition.
 4. The shunt system of claim 3 wherein the externaldevice is a hand-held signal processing member that transdermallymeasures the signal from the sensor assembly.
 5. The shunt system ofclaim 1 wherein the implantable housing comprises a recessed portionadjacent the sensor assembly, the recessed portion having a shapecomplimentary to an outer surface of an external device for reading asignal output by the sensor assembly such that the external device canbe positioned within the recessed portion when the implantable housingis within a body to detect the signal output by the sensor assembly andidentify a shunt malfunction.
 6. The shunt system of claim 1 furthercomprising: a proximal catheter fluidly coupled to the inlet port and adistal catheter fluidly coupled to the outlet port, and wherein fluidflows into the implantable housing through the proximal catheter and outof the implantable housing through the distal catheter.
 7. An apparatusfor monitoring fluid flow through an implantable shunt comprising: apressure sensitive valve capable of controlling flow of fluid through animplantable shunt housing; a rotor assembly fluidly coupled to thepressure sensitive valve, the rotor assembly capable of rotating asfluid flows through the pressure sensitive valve; and a generatorcoupled to the rotor assembly, the generator having an inductive coilthat generates a signal based on the rotating of the rotor assembly,wherein the signal is indicative of a condition of the shunt.
 8. Theapparatus of claim 7 wherein the rotor assembly is positioned downstreamfrom the pressure sensitive valve such that the signal is generated whenfluid flows through the pressure sensitive valve
 9. The apparatus ofclaim 7 wherein the generator is mechanically actuated.
 10. Theapparatus of claim 7 wherein the condition of the shunt is a malfunctionwhen the signal indicates a period of fluid flow and a period ofnon-fluid flow different from a predetermined control period of fluidflow and period of non-fluid flow.
 11. A method for detecting acondition of an implantable shunt comprising: detecting a flow of fluidthrough an implantable shunt; generating a signal indicative of a periodof fluid flow through the implantable shunt based on the detecting; andoutputting the signal to an external device capable of determining, fromthe signal, whether the shunt is malfunctioning.
 12. The method of claim11 further comprising: identifying a location of the shunt malfunctionfrom the signal.
 13. The method of claim 11 wherein the signal isgenerated by a mechanically actuated sensor assembly.
 14. The method ofclaim 11 wherein the signal is generated by a radio-frequencyidentification tag.
 15. The method of claim 12 wherein the location ofthe malfunction is at a pressure sensitive valve associated with theshunt.
 16. The method of claim 12 wherein the location of themalfunction is at a distal portion of the shunt.
 17. The method of claim12 wherein the location of the malfunction is at a proximal portion ofthe shunt.
 18. The method of claim 11 wherein the signal indicates afirst period of time corresponding to the period of time the pressuresensitive valve is in an open position and a second period of timecorresponding to a period of time between the open position and a closedposition of the pressure sensitive valve.
 19. The method of claim 18wherein the first period of time and the second period of time arecompared to a control signal to determine whether the shunt ismalfunctioning.
 20. A shunt system comprising: an implantable housinghaving a proximal end and a distal end, wherein a fluid inlet port isformed in the proximal end and a fluid outlet port is formed in thedistal end; a pressure sensitive valve contained within the housing at aposition between the proximal end and the distal end, the pressuresensitive valve capable of controlling a flow of fluid between the fluidinlet port and the fluid outlet port; and a sensor assembly coupled tothe pressure sensitive valve, wherein the sensor assembly comprises anRFID tag operable to communicate information indicative of a status ofthe pressure sensitive valve.
 21. The shunt system of claim 20 furthercomprising an external reading device having an active RFID readeroperable to read a communication from the RFID tag and determine whetherthe valve is open or closed based on the communication.